Non-contact optical coherence tomography imaging of the central and peripheral retina

ABSTRACT

A system includes a mirror having an axis extending through a central portion thereof, and a portion of the mirror being configured to repeatedly oscillate between a first position and a second position around the axis, so as to record a field of up to 200 degrees of a portion of the central and peripheral retina, a first scanner configured to use a spectral domain optical coherence tomography system to obtain a non-contact wide angle optical coherence tomography-image of the portion of the central and peripheral retina, and a second scanner configured to obtain an image of the retina, wherein the mirror is configured to oscillate so as to move the focal point of the mirror from one side of a pupil to another side, thereby permitting scanning light inside the eye to cover a predetermined peripheral field, thus creating a two dimensional or three dimensional image of the field.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.12/492,491, filed Jun. 26, 2009, the entirety of which is incorporatedherein by reference.

BACKGROUND

1. Field of Invention

The present invention relation to a system for Non-contact OpticalCoherence Tomography (OCT) imaging of the central and peripheral retina.

2. Related Art

Ophthalmic Optical Coherence Tomography (OCT) of the eye was originallydeveloped by obtaining cross-sectional images of the sensory retina andretinal pigment epithelium. Recently, spectral domain OCT becameavailable, a new technique that allowed major improvements particularlyregarding image acquisition speed and image resolution. However,existing instruments do not scan the retinal periphery. The OCT scan istypically restricted to the central <40° of the retina.

OCT is presently used (in ophthalmology) to evaluate only either thethickness of the central retina in macular diseases or separately thestatus of the optic nerve head in glaucoma patients. Furthermoreobtaining the OCT pictures require dilatation of the pupil prior totaking pictures. OCT can not be performed in patients with a constrictedpupil; since presently available optics do not permit it. In conventionsystems, the existing unbearable reflexes created by their opticalelements make it impossible for the operator to simultaneously see theretina and focus on the desired area (e.g., the macula or the OpticNerve head). In addition, the field of view is very limited; thus,important regions in the peripheral retina can not be visualized withcurrent OCT systems and the system needs a skilled personal to handlethe instrument.

Present OCT systems generally employ a Fundus Camera Design. A funduscamera is a complex optical system for imaging and illuminating theretina. Due to its location the retina must be imaged and illuminatedsimultaneously by using optical components common to the imaging andillumination system.

Conventional Fundus Cameras used for OCT generally include an objectivelens which forms an intermediate image of the retina in front of a zoomlens, designed to accommodate for the refractive error of the patient,which relays the intermediate image to the CCD. Light travels throughthe objective lens in both directions making the consideration of backreflections important. On the illumination side, the objective lensimages an annular ring of light onto the pupil; therefore, the need fordilation of the pupil. This ring of light then disperses to give a nearuniform illumination of the interior retinal surface. The objective lensalso serves a role in the imaging optics. It captures pencils of lightemanating from the eye and forms an intermediate image of the retina.This intermediate image is then relayed by additional optics to adigital imaging sensor or film plane.

The objective lens also serves as the limiting factor in the field ofview of the camera. FIG. 1 shows the relationship between the objectivelens and the eye.

Bundles of rays leaving the periphery of the retina emerge from theemmetropic eye as a roughly collimated bundle of rays. This bundle mustpass through the edge of the objective lens in order to become part ofthe fundus image. Bundles coming from more eccentric points on theretina cannot be captured by the objective and therefore cannot be seenin the fundus image. One method of increasing the field of view in thisconventional configuration is to increase the size of the objective lensas seen in FIG. 2.

However, increasing the diameter of the objective lens causes anincrease in the aberration of these lenses with size. Current practicallimits taking this approach lead to a roughly 40-degree field of viewseen in modern fundus cameras. An alternative method for increasing thefield of view is to move the objective lens closer to the eye which hasalso its own limitations. The extreme case for this technique is where aportion of the objective lens actually comes in contact with the cornea.One drawback to this configuration is patient aversion due to theproximity of the lens, and increased risk of infection and cornealabrasion.

SUMMARY OF THE INVENTION

The embodiments of the present invention overcome the above problemswith the conventional systems.

One objective of the present invention is to develop a non-contact widefield OCT system to extend the field of view >200 degree and can beperformed in un-dilated pupil.

This invention can provide access to the retinal periphery andsimplifies taking images. These sections of the retinal periphery mayprovide important information about the diseased areas of the peripheralretina permitting evaluation and potential treatment. Additionally, thepresent invention enables ophthalmologists to visualize and diagnose avariety of ailments including glaucoma, macular degeneration, retinaldetachment, and diabetic retinopathy and all peripheral retinaldiseases. The OCT system of the present invention can utilize lowcoherent visible or preferably infra red wave lengths of up to 10640 nm.The OCT system of the present invention can also makes a patient'sexamination easier by eliminating the time spent to dilate the patientspupil and reducing the focusing time, which improves the patient'stolerance of the procedure since a wide-field fundus photograph can begenerated with the same infrared light without blinding the patient withvisible light.

In conventional systems no information can be obtained from thevitreoretinal interface in the retinal periphery which is main cause ofretinal tear and retinal detachment which is one of the main cause ofblindness more frequently in near sighted patients. What is needed is awide-field retinal imaging OCT system that extends the fields ofview >200 degree field.

Additional features and advantages are described herein, and will beapparent from, the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a conventional objective lens positioned adjacent aneye;

FIG. 2 illustrates an objective lens having an increased diameter;

FIG. 3 illustrates an embodiment of the present invention in which themirror is configured, if needed, to wobble or rotate around the visualaxis;

FIG. 4 illustrates an embodiment of the present invention in which acentral part of the mirror can be switched automatically to achieve thebeam diversion see attached; and

FIG. 5 illustrates an embodiment of the present invention that includestwo scanners.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention may include imaging modalities,such as optical coherence tomography, snapshot imaging Polarimetry andcomputed tomography imaging spectrometer. Additionally, White Light LED,infra red diodes, Nd-YAG as an illumination source, can each maintainexcellent image quality across the field of view.

Spectral Domain Optical Coherence Tomography, OCT, operates insubstantially the same manner as a low coherence Michelsoninterferometer. That is, light from a broadband source is separated intoa reference and sample arm. Reflected light from both arms is recombinedin the detection arm to form interference fringes when the optical pathdifference between sample and reference arms is within the coherencelength of the source. The signal produced by the detection ofinterference fringes is proportional to the backscatter from the depthstructure of the sample. Spectral components of the light in thedetector arm are separated by a spectrometer allowing for the detectionof interference fringes at different wavelengths corresponding todifferent optical path differences representing depth information.Structural depth information from the sample is recovered by a FourierTransform of the spectral data allowing for optical sectioning of thesample. Swept Source OCT operates by replacing a broadband source with arapidly scanning source that sweeps across a large range of wavelengths.The detector records the backscattered signal for each wavelength andposition. By utilizing this methodology the recovered signal isequivalent to Spectral Domain OCT. Swept Source OCT allows for fasteraxial scanning than conventional Spectral Domain OCT and eliminates theneed for a high performance spectrometer. Light from the swept source iscoupled into a fiber coupler that separates the light into the referenceand sample arms of the OCT system. The reference arm of the OCT systemconsists of a collimating lens, a block of material for compensating thematerial dispersion of the source and fixed mirror. Light entering thereference arm is collimated, passes through the dispersion compensatingmaterial is reflected by the fixed mirror back through the dispersioncompensating material and is coupled into the fiber coupler. The samplearm of the system, responsible for imaging the retina, consists of scanmirrors, an afocal relay, a wide field of view through a concave and orelliptic mirror and subject's eye. The Oct images can be also convertedinto two dimensional of the retina by the computer soft ware.

The embodiments of the present invention may utilize a concave mirror 10(circular or elliptical) that focuses a beam of light 12 toward itsfocal point located inside the patient's pupil (of 2-6 mm or largerdiameter). The beam scanner and receivers are attached to the mirror. Asshown in FIG. 3, the mirror can, if needed wobble, (or oscillate)slightly. This wobbling moves the focal point of the mirror slightlyfrom one side of the pupil to the other side permitting the scanninglight (low coherent wave lengths etc.) inside the eye to cover a largerperipheral field than possible without oscillation. Because theoscillation of the beam can be >1000× faster than the oscillation of themirror, an expanded retinal field may be achieved, even if some of thebeam is clipped by the pupil.

It is generally not possible to wobble (i.e., oscillate) rapidly a heavyfundus camera, nor would such wobbling significantly move the camera'sview inside the eye. Additionally, a strip of an elliptical can berotated along its axis if an emitter is attached to the mirror. Thisrotation may eliminate the need of an emitter oscillating in a circularfashion, since the elliptical mirror can rotate 360 degree thus coveringthe entire field of fundus.

Embodiments of the present invention also can have two emitters 14 and16 and receiver arms 18 and 20 positioned in different areas withrespect to the above mentioned concave mirror (FIG. 3). In theseembodiments, a central OCT may be easily achieved, and then can berapidly switched to a larger peripheral one. Both are preferablyattached to the concave mirror 10, one central in front of the pupil forcentral scanning alone and one peripheral where the beam is reflectedoff the concave mirror before entering in the eye. These two arms 18 and20 can be switched from one to the other electronically or manually, ifdesired. As illustrated in FIG. 4, a small central part 22 of the mirror10 can be switched automatically to achieve the beam diversion. However,if desired the peripheral arm can be used alone.

Light entering the sample arm can be collimated and directed to a scanmirror responsible for sweeping the beam along the x axis. An afocalrelay can direct the beam deflected by the x axis scan mirror to anotherscan mirror responsible for sweeping the beam along y axis. The y axisscan mirror can direct the beam to a wide field of view of a concavemirror or an elliptical mirror positioned in front of the subject's eye.This combination of scan mirrors, afocal relay and a wobbling-rotateableconcave mirror or an elliptical mirror placed in front of the patientseye and an OCT system allows for three dimensional volumetric imageacquisition over 200 degree field of the retina. Light incident to theretina is back scattered by retinal structures and propagates backthrough the scanning system and coupled into the fiber coupler. Lightfrom the reference and sample arms is combined in the detection arm ofthe system producing interference fringes at the detector. Detection ofthe interference fringes is synchronized with the propagation of thespecific wavelength coupled in the system by the swept source and theposition of the x and y axis scan mirrors provides the desired wideangle OCT of the, central and peripheral retina. This method providesnot only information on the retinal structure (thickness, degeneration,erosion, holes etc) but also the vitreoretinal interface, such aspersistent vitreoretinal attachments and tractions on the retina. Theuse of a circular concave mirror, or preferably an elliptical mirror,permits us to place the focal point (or the second focal point of anelliptical mirror) at the pupil or further in a posterior plane insidethe eye permitting the scan to pass with ease through a small pupilwhile larger area of the retina are being scanned. The central part ofthese mirrors can also be replaced by a transparent glass so that acentral OCT scan can be obtained initially from limited central area.(FIG. 3 A, B, C). As soon as an image is obtained from the retina thecentral part of the mirror can be replaced automatically by the secondscanner reflecting the light off the concave mirror and scanning andacquisition is obtained from this separate line which gives a wide angleOCT, imaging including the entire retina.

After positioning the patient's head in front of a head holder, used forfundus photography, the OCT system can be moved toward the eye. Once theretina is visualized with the infrared beam through the central(transparent) part of the concave mirror, the central part can beswitched with equal size mirror and the other arm of the OCT system canbe activated which records rapidly a circular field of 120-200 degree,depending on the mirror used. Alternatively, the central part can alsobe made with a partial reflecting mirror which would eliminate actualphysical exchange of the central part. The data collected can beanalyzed and compared with ophthalmoscopic examinations and fundusphotography done on each patient. Embodiments of the present inventionare also capable of providing a black and white fundus picture. The scancan be modified to provide a false color image of the retina and itsinterface. The OCT according to embodiments of the present invention isnot only capable of providing a cross sectional view of the entire areaincluding the Optic Nerve head, Vitreoretinal adhesions, but also canprovide an elevation map of the scanned field. The information gained isinvaluable for decision making prior to vitreoretinal surgery, and laserapplication in patients with diabetic retinopathy, macular degeneration,glaucoma , inherited retinal degeneration, retinal diseases predisposingto a retinal detachment etc.

The same system can be used for obtaining wide angle OCT of the corneaand the anterior segment of the eye including the lens by moving themirror away from the eye.

As shown in FIG. 5, another embodiment of the present can include asecond scanner. In this embodiment, the second scanner is capable ofemitting a white light source for digital photography of the retina (orthe cornea, depending on the position of the mirror's secondary focalpoint). The second scanner is also capable of storing and processinginformation obtained and presenting the information in 2D or 3D formaton a computer screen.

Additionally, in one embodiment, the scanner is equipped with multiplelaser beams to obtain an image of the retina with three compensatorycolors, green, red, and blue or infrared, if desired. A filter that is500 nm, along with the blue wave length can be used for flouoresceinangiography or another filter at 800 nm for indicyanin greenangiography. These diagnostic images can be transmitted, as is known inthe art, to a fundus camera etc. and digital image can be stored. Theimages can be presented on a touch screen monitor to evaluate specificarea of the fundus using diagnostic photos, superimposed on the OCTimages; obtained from the OCT scanner using an image processor, creating2-3 D images of any part of the central and/or peripheral retina, etc.,which can be selected on the touch screen monitor and can be used todemonstrate the cornea, anterior chamber or the lens in 2-3D format.

In another embodiment, the second scanner is equipped with at least oneor more high power lasers (elecrtomagnetic waves) having wavelengths ofabout 192 nm to 3.9 micron. The lasers are capable of producing the riseof the tissue temperature to the desired hyperthermic effect,coagulative or photoablative effect. Moreover, the second scanner can bearmed with one or more powerful coagulative lasers (having differentwave lengths) to apply scatter laser lesions in the retina.

In one embodiment the areas to be coagulated can be selected on thetouch screen monitor having 2-3 D format, which results in applying veryshort pulses of laser delivered in a short time to cover a part or allof the retina except for the macula area.

Furthermore, the desired area of the retina or the cornea can be markedon the touch sensitive screen, including or excluding an area from thethermal effect, ablative effects of the laser.

Additionally, in one embodiment, the invention is capable of remoterecording and transmission of the information, via the internet or anyother suitable transmission medium. Thus, the person performing theprocedure can be located in a different locale, or multiple people invarious locations can watch and/or assist in the procedure.

In another embodiment, an ultrasonic arrays transducer can placed on thelid for producing and receiving ultrasonic pulse of 500 Hz-80 MHz, whichcan be useful for acoustic spectroscopy and data storage for creating a2-3 D format of the photoacoustic image of an area.

In such an embodiment, the invention would be capable of recordingphotoacoustic information at 100-10 MHz where a heat energy creates aphoto-acoustic sound capable of measuring of the tissue temperature riseafter laser application and a means or device cable of connecting andcontrolling the desired thermal effect using computer software thatgives feed back to the laser to maintaining the desired tissuetemperature by modifying instantly the laser energy level per pulse.

In one embodiment a third scanner/laser can be used. In this embodiment,the second laser can, for example, emit white light, and the third laserenables a rise in tissue temperature to the desired hyperthermic,coagulative and/or photoablative effect.

In each of the embodiments discussed above, one of a concave mirror oran elliptical mirror having an axis extending through a central portionthereof, is configured to repeatedly oscillate or wobble between a firstposition and a second position around the axis, so as to record a fieldof up to 200 degrees of a portion of the central and peripheral retina.If desired a central portion of the mirror (e.g., about 1 mm to 6 mm,and preferably about 5 mm) can be disconnected, so as to oscillaterelative to the remainder of the mirror. The oscillation speed can varydepending on the speed selected by the person performing the procedure.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. A system for imaging of the central and peripheral retina,comprising: one of a concave mirror and an elliptical mirror having anaxis extending through a central portion thereof, and at least a portionof said one of a concave mirror and an elliptical mirror beingconfigured to repeatedly oscillate between a first position and a secondposition around the axis, so as to record a field of up to 200 degreesof a portion of the central and peripheral retina; a first scannerconfigured to use a spectral domain optical coherence tomography systemto obtain a non-contact wide angle optical coherence tomography-image ofthe portion of the central and peripheral retina; and a second scannerconfigured to obtain an image of the retina, wherein the one of aconcave mirror and an elliptical mirror is configured to oscillate so asto move the focal point of the one of a concave mirror and an ellipticalmirror from one side of a pupil to another side, thereby permittingscanning light inside the eye to cover a predetermined peripheral field,thus creating a two dimensional or three dimensional image of the field.2. A system according to claim 1, wherein said second scanner isconfigured to emit white light capable of digital photography.
 3. Asystem according to claim 1, wherein said second scanner includes afirst, second and third laser beam capable of obtaining an image usinggreen, red and blue light, respectively.
 4. A system according to claim3, wherein said second scanner includes a 500 nm filter for the bluelight and a 800 nm filter for the green light.
 5. A system according toclaim 1, wherein said second scanner includes a laser capable ofemitting electromagnetic waves having a wavelength between about 192 nmto about 3.9 microns.
 6. A system according to claim 1 wherein saidsecond scanner is configured to produce a rise in temperature so as tocreate a hyerthermic, coagulative or photoablative effect.
 7. A systemaccording to claim 1, further comprising a touch screen display deviceconfigured to display a desired area of the fundus.
 8. A systemaccording to claim 1, wherein a device configured to transmit the twodimensional or three dimensional image of the field to a separatelocation.
 9. A system according to claim 9, further comprising anultrasonic array transducer configured to by placed on an eyelid andproduce and receive ultrasonic pulses so as to be useful in acousticspectroscopy and data storage for creating the two dimensional or threedimensional image.
 10. A system according to claim 9, wherein saidultrasonic transducer is configured to record photoacoustic informationat 100-10 MHz where heat energy creates a photoacoustic sound capable ofmeasuring of the tissue temperature rise after laser application andconfigured to connect and control a thermal effect using computersoftware that gives feed back to the second scanner to maintain adesired tissue temperature by modifying the laser energy level perpulse.
 11. A system according to claim 1, wherein said at least aportion of said one of a concave mirror and an elliptical mirror is acentral portion.
 12. A method for imaging of the central and peripheralretina, comprising: repeatably oscillating at least a portion of one ofa concave mirror and an elliptical mirror between a first position and asecond position around an axis extending through a central portion ofthe one of a concave mirror and an elliptical mirror, so as to record afield of up to 200 degrees of a portion of the central and peripheralretina, obtaining a non-contact wide angle optical coherencetomography-image of a portion of the central and peripheral retina via ascanner using a spectral domain optical coherence tomography systemusing a first scanner, and obtaining a digital image of the retina usinga second scanner, wherein the oscillating one of a concave mirror and anelliptical mirror around an axis includes oscillating the one of aconcave mirror and an elliptical mirror around the axis so as to movethe focal point of the mirror from one side of a pupil to another side,thereby permitting scanning light inside the eye to cover apredetermined peripheral field, thus creating a two dimensional or threedimensional image of the field.
 13. A method according claim 12, saidsecond scanner emits white light capable of digital photography or emitsgreen, red and blue light.
 14. A method according to claim 13, furthercomprising filtering the blue light with a 500 nm filter and filteringthe green light with a 800 nm filter.
 15. A method according to claim12, wherein emitting electromagnetic waves having a wavelength betweenabout 192 nm to about 3.9 microns using a laser in the second scanner.16. A method according to claim 12, further comprising displaying adesired area of the fundus on a touch screen display device.
 17. Amethod according to claim 12, further comprising transmitting the twodimensional or three dimensional image of the field to a separatelocation.
 18. A method according to claim 12, further comprising placingan ultrasonic array transducer on an eyelid and to produce and receiveultrasonic pulses so as to be useful in acoustic spectroscopy and datastorage for creating the two dimensional or three dimensional image. 19.A method according to claim 18, wherein said ultrasonic transducerrecords photoacoustic information at 100-10 MHz where heat energycreates a photoacoustic sound capable of measuring of the tissuetemperature rise after laser application and configured to connect andcontrol a thermal effect using computer software that gives feed back tothe second scanner to maintain a desired tissue temperature by modifyingthe laser energy level per pulse.
 20. A method according to claim 12,wherein said oscillating at least a portion of said one of a concavemirror and an elliptical mirror includes oscillating a central portionof said one of a concave mirror and an elliptical mirror.